/Engine/Source/Runtime/Core/Public/HAL/ThreadSingleton.h
sets the TLS store to the instance and returns the previous instance.
static [FTlsAutoCleanup](API\Runtime\Core\HAL\FTlsAutoCleanup) * Inject ( [FTlsAutoCleanup](API\Runtime\Core\HAL\FTlsAutoCleanup) * Instance, uint32 & TlsSlot )